1. Field of the Invention
The present invention relates to a multi-plate clutch system comprising: a clutch outer connected to an input member; a clutch inner connected to an output member; a plurality of driving friction plates engaged with the clutch outer movably in an axial direction, and unrotatably relative to the clutch outer; a plurality of driven friction plates alternately overlapped with the driving friction plates, and engaged with the clutch inner movably in the axial direction, and unrotatably relative to the clutch inner; a pressure plate movable in the axial direction to bring the driving friction plates and the driven friction plates into pressure contact with each other, thereby frictionally engaging the driving friction plates and the driven friction plates together; a clutch spring for biasing the pressure plate in a direction in which the driving friction plates and the driven friction plates are brought into pressure contact with each other; and at least one of assist means and slipper means, the assist means configured to increase a pressure contact force produced by the pressure plate when torque is changed for acceleration, the slipper means configured to decrease the pressure contact force produced by the pressure plate when the torque is changed for deceleration.
2. Description of the Related Art
Through Japanese Patent Application Laid-open No. 2008-38954, a multi-plate clutch system including assist means and slipper means is known in which: a boss part of a center cam plate fixed to an output shaft and being common to the assist means and the slipper means is slidingly fitted to an assist cam plate and a slipper cam plate which are fixed to a clutch inner with bolts to be unmovable relative to the clutch inner in an axial direction; thereby, the rotational center of the clutch inner is aligned with the respective rotational centers of the output shaft and the center cam plate; and the boss part of the center cam plate includes oil holes for supplying oil to the sliding portion between the assist cam plate and the boss part, as well as between the slipper cam plate and the boss part.
Meanwhile, there is an idea that, for the purpose of securing the centering for aligning the rotational center of the clutch inner with the rotational centers of the output shaft and the center cam plate, the inner peripheral surface of the clutch inner is put in sliding contact with and is supported by the outer peripheral surface of the center cam plate. To this end, the slidability needs to be secured by sufficiently supplying oil to the sliding contact portion between the clutch inner and the center cam plate. However, if the technique disclosed in Japanese Patent Application Laid-open No. 2008-38954 is simply applied to this, a problem occurs in which: oil supplied from the oil holes is retained in the concave cams in the center cam plate; and a sufficient amount of oil cannot be supplied to the sliding contact portion.